Conventional remote center compliance devices use a set of at least three shear pads, or two sets of at least three pads each, to provide rotational and translational compliance and are then arranged so that a dead load places them all in tension. It was assumed in the past that each pad's compression/tension stiffness was much greater than its shear stiffness, and that the stiffness ratio, compression axial stiffness or tension axial stiffness compared to shear stiffness, remained the same throughout normal use. Remote center compliance devices were generally not regarded as being in tension, or tension was not recognized as a source of problems.
However, in such remote center compliance devices using three and six shear pad flexure units, the center of compliance was always much closer to the device than desired and predicted analytically. Further, in use under normal lateral deflection, the remote center would move even more dramatically closer.
In addition, such remote center compliance devices were suffering breakage of their shear pads even though the dead load on them did not exceed their rated loading.